Other positives to employers are H1Bs will work extra hours
I don't know many business professionals who work less than 60 hours a week.
will not be inclined to invoke civil rights benefits (e.g. FMLA)
I don't know anyone in the private sector who has taken advantage of the FMLA. I know a few people who have used it, but they are either in government or academe.
do not incur pension liability
What's a pension? Most private sector employers have long since shifted to 401Ks, particularly for newer employees.
and will not generally enter union membership
Outside of teachers, I don't know a single professional who is in a union.
60 hours a week? How about 80+?
Unbelievable you haven't seen FMLA usage. Anyone that is pregnant and who earns sick leave as part of their compensation package, is eligible to take up to 12 weeks at least, of leave and to be paid for however long their sick leave accrual covers. BTW I find nothing wrong with FMLA.
Savvy pros view 401ks as junk. Tax deferred whole life insurance plans as part of a retirement plan are much superior.
The main advantage to employers is 2+ for 1.
If the US Gov is allowing several hundred thousand professional work visa annually, then over years there is an accumulation of several million such workers into the workforce. If there are say 4 million critical skill foreign workers in the US earning an average of 60k replacing 2 million resident workers that would earn 120k, the increase in FICA is:
14% of (4M x 60k - 2M x 80k) = 11.2 billion
to Social Security.
The 1040 income tax differences are irrelevant because 1040 income taxes go to paying interest on national debt issues out of thin air by the 'Federal' Reserve (a private cartel of bankers, nothing 'federal' about it).
http://video.google.com/videoplay?docid=-4312730277175242198
1.5 hours long but worth every minute and then some in repetition for study.